1. Field of the Invention
The present invention relates to a skate having a height adjustment mechanism which enables the heel of the skate to be raised or lowered, thus shifting the skater's center of gravity.
2. Description of Related Art
A variety of ice and roller skates are commercially available and used for recreational and transportation purposes. For example, different types of ice-skates are available which are designed to be particularly adapted to purposes including figure skating, speed skating or hockey playing. Additionally, both traditional roller-skates having two rows of two wheels each, and in-line roller-skates having one centrally arranged row of wheels, are available.
It has been found that for a variety of reasons, adjustment of the angle of the skate boot relative to the ground, such that the skater's center of gravity is shifted forward or rearward, is desirable. In particular, when playing hockey it has been found that offensive players or "forwards" may wish to shift their center of gravity forward, such that their weight is on their toes, in a manner which enables quick acceleration in a forward direction. By contrast, defensemen who often skate backwards may prefer to shift their centers of gravity rearwards, such that their weight is on their heels. One means of allowing such adjustment to ice-skates is described by U.S. Pat. No. 3,988,124 to Babcock, wherein the metal skate blade is ground down on one end or the other to change the skate's orientation with the ice. This method suffers a disadvantage, however, in that once the blade has been ground to a particular contour, it cannot be readily adjusted without replacement or regrinding of the blade. This is particularly troublesome for "utility players" who may play a number of positions, including both offensive and defensive roles. Additionally, this method is inapplicable to roller-skates, which do not have a blade capable of adjustment by grinding.
U.S. Pat. No. 5,253,884 to Landers discloses a lever means for adjusting the height of individual rollers of an in-line roller-skate. An axle bearing is located eccentrically within a rotateable bushing, which moves relative to the skate frame by means of a lockable lever, to raise or lower a skate wheel. By raising one or more skate wheels, other wheels no longer contact the ground, thus enabling the skater to execute turns more quickly. This arrangement may be desirable for certain applications such as figure skating or stunt skating, however, for most general applications a more stable and rugged construction having all wheels in contact with the ground is desired.
Such an arrangement is envisioned by U.S. Pat. No. 5,257,793 to Fortin. Fortin describes a skate assembly having a telescopic member mounted to the heel of the skate boot to allow adjustment of the boot's angle relative to the floor or ice. The telescopic member is extended and retracted by rotating a threaded cylinder which engages a threaded pedestal fixedly mounted to the skate's heel. It has been discovered that in operation, the Fortin device creates undesirable stresses and bending moments in the device's elements. Analyzing the Fortin skate as a three-link mechanism (the blade member, the boot, and the threaded cylinder) with two pin joints (heel end of blade member to threaded cylinder, toe end of blade member to toe end of boot), and one slide joint (heel end of boot to threaded cylinder), by Gruebler's equation: ##EQU1## where n is the number of links and f.sub.1 is the sum of pin and slide joints, shows the Fortin device to possess zero degrees of freedom. See Arthur G. Erdman and George N. Sandor, 1 MECHANISM DESIGN: ANALYSIS AND SYNTHESIS, 16-24 (Prentice-Hall 1984). Thus, raising the skate's heel by extending the threaded cylinder of the Fortin skate causes stresses within the device's elements and a bending moment on the skate boot. This bending moment is generally not problematic when the Fortin device is applied to skates having traditional flexible leather boots. Modern skates, however, are often constructed with a rigid plastic boot for increased ankle support and impact protection. If the Fortin device is used with these rigid boots, unacceptable stress damage to the boot or the mechanism can result.